Cutting tools used in metal cutting machines such as lathes, drills, milling machines and the like, are frequently formed with a removable and replaceable cutting tool insert made of a hardened material such as high speed steel, carbide or ceramic, mounted upon the tool holder. The inserts are generally formed having rectangular, triangular, diamond or circular cross-sectional configurations. Such inserts are formed with a number of cutting edges so that when one edge becomes worn the insert may be rotationally indexed to present a new cutting edge. When all the edges of a insert are worn, the insert is replaced.
Conventionally, such indexing of a cutting tool insert has been performed either manually or by relatively complex indexing means. Typically when a cutting edge of an insert has been used or worn the machining operation is temporarily suspended, the insert is loosened on its holder, then turned to present a new cutting edge to the work piece, accurately positioned, and then retightened on the holder. Indexing of a cutting tool insert, therefore results in an undesirable loss of operating time.
Furthermore, with the advent of computer-aided manufacturing systems, improved means for indexing tool inserts with increased speed while maintaining accuracy of position is desirable.
One attempt at providing an indexable cutting tool is disclosed in U.S. Pat. No. 4,552,046 (Dombrowski et al). In this patent a cutting tool insert is automatically indexed by means of a shaft and slideable member attached to the tool holder. The slideable member engages a point of the insert and pushes it in a rotational manner until the next insert point is in the cutting position. The insert is locked in position using one surface of the insert against the sliding member. This device, while providing for automatic indexing of the insert provides only one locking surface for the insert thereby making it susceptible to loosening during operation.
Thus, there is a need for a cutting tool having an insert which may be automatically rotationally indexed while providing an improved securing means for the insert to prevent both loosening and damage to the workpiece during operation.